2018 10.5 2017 9.6 2016 9.5 2015 9.9 2014 10.3 2013 8.7 2012 9.1 2011 9.6 2010 7.6 2009 9.2 2008 9.5 2007 9.9 2006 9.5 2005 9.0 2004 8.9 2003 9.4 2002 9.6 2001 9.0 2000 9.9 1999 9.5 1998 9.1 1997 8.9 1996 7.2 1995 8.9 1994 9.7 1993 8.5 1992 9.4 1991 8.4 1990 9.5 1989 9.5 1988 9.1 1987 7.4 1986 7.9 1985 7.4 1984 8.0 1983 9.0 1982 8.9 1981 8.2 1980 7.6 1979 7.7 1978 7.8 1977 8.7 1976 8.5 1975 8.9 1974 8.8 1973 8.2 1972 7.8 1971 8.4 1970 7.7 1969 7.8 1968 8.2 1967 8.9 1966 8.5 1965 7.5 1964 8.1 1963 7.1 1962 7.1 1961 9.0 1960 8.4